The decay of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tb}$ to levels of ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$ has been studied by $\gamma$-ray and conversion-electron spectroscopy with mass-separated sources. Below 660 keV, approximately 150 $\gamma$ rays have been observed and assigned to a level scheme with 28 levels. The mixing of even-parity levels is calculated using a variation plus diagonalization procedure. The resultant wave functions are used to calculate transition probabilities and magnetic moments, which are compared with the experimental results. $\beta -$ and $\gamma -$ vibrational states are identified and compared with corresponding excitations in neighboring even-even nuclei.

RADIOACTIVITY ${}_{}{}^{155}{}_{}{}^{}\mathrm{Tb}$ [from ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}\mathrm{}(p,n)\mathrm{}$, ${}_{}{}^{153}{}_{}{}^{}\mathrm{Eu}(\alpha ,2n)$, ${}_{}{}^{154}{}_{}{}^{}\mathrm{Gd}(\alpha ,3n)$ ${}_{}{}^{155}{}_{}{}^{}\mathrm{Dy}$(EC)]; measured $E_{\gamma }$, $I_{\gamma }$, $I_{\mathrm{ce}}$. ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$ deduced transitions, ICC, multipolarities, levels $J$, $\pi$, Nilsson assignments. ${}_{}{}^{155}{}_{}{}^{}\mathrm{Gd}$ calculated wave functions, transition probabilities, magnetic moments. Ge(Li), Si(Li) detectors, Compton suppression spectrometer, mass-separated sources.

• Received 11 August 1975

DOI:https://doi.org/10.1103/PhysRevC.13.2466